Pension and Other Post-Retirement Benefits - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plans, employer matching contribution, percentage	50.00%
Defined contribution plans, employer matching contribution of eligible salary, percentage	6.00%
Defined contribution plans, charges incurred	$ 0.7	$ 1.0	$ 0.7
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plans, pension expenses	0.5	0.4	0.4
Defined benefit plans, benefit obligation	8.3	7.3	5.0
Defined benefit plans, Net liability	$ 7.1	$ 6.8	$ 4.2

Amount of liability, recognized in statement of financial position, for defined benefit pension plan. Excludes other postretirement benefit plan.

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-Publisher FASB
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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

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Amount of cost for defined contribution plan.

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Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

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Percentage employer matches of the employee's percentage contribution matched.

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Amount of cost (reversal of cost) for pension benefits. Excludes other postretirement benefits.

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